Compositions and methods for treating wastewater

ABSTRACT

Compositions and methods and systems for treating wastewater within a wastewater treatment system of described. In an embodiment, a composition for treating wastewater within a wastewater treatment system and for preventing or reducing the occurrence of struvite scale formation within the wastewater treatment system may include an admixture including a magnesium compound. The admixture may also include a dispersing agent. The admixture may further include at least one of a free magnesium control agent and a seed material. Other compositions and methods are described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patentapplication Ser. No. 61/805,335 entitled “Reducing And PreventingStruvite Scale Formation In Waste Water Treatment Using A MagnesiumHydroxide Slurry,” filed on 26 Mar. 2013, this application also claimsthe benefit of U.S. provisional patent application Ser. No. 61/703,011,entitled “Reducing and Preventing Struvite Scale Formation in a WasteWater Treatment Using a Magnesium Hydroxide Slurry,” filed on 19 Sep.2012, the entire disclosures of which is incorporated herein byreference.

TECHNICAL FIELD

The present disclosure generally relates to compositions and methods fortreating wastewater, and more particularly to compositions and methodsfor reducing and/or preventing the formation of struvite scale withinwastewater treatment systems.

BACKGROUND

Wastewater treatment systems, such as municipal and commercialwastewater treatment systems may provide for the treatment of wastewaterfrom residential, commercial, or other uses. Wastewater treatmentsystems may variously include wastewater collection systems and/orwastewater treatment facilities. Generally, a wastewater collectionsystem may receive wastewater from a point of use, such as a residentialhome, a business, and/or commercial facility and may transport thewastewater to a wastewater treatment facility. The collected wastewatermay be transported using any combination of gravity conveyance andpumping to transport the wastewater from various collection points to,and even through, a wastewater treatment facility. Generally, awastewater treatment facility may include one, or a variety, oftreatment processes that may, for example, separate solid materials,biomaterials, and the like from the water and/or may perform otherprocesses that may render the processed wastewater suitable to rejointhe environment, such as an environmental water supply, like a river orlake, or an environment land-based return.

The operation and efficiency of a wastewater treatment system may beinfluenced by a variety of factors, including factors that may impactthe ability to collect and/or transport the wastewater, may impact theability to carry out wastewater treatment processes, and/or impact theservice and/or maintenance requirements and time of wastewatercollection and/or processing systems and equipment. Factors that mayimpede the transport of wastewater throughout the system, decrease theefficiency of treatment processes, and/or increase service ormaintenance requirements of the wastewater treatment system may increasethe operating cost of the wastewater treatment system. For example, adecrease in efficiency may result in increased energy costs to operatethe wastewater treatment system and/or a decreased throughput of thewastewater treatment system. An increase in the required service andmaintenance may result from expenditures in equipment repair andreplacement and the number of maintenance man-hours that may be requiredto keep the wastewater treatment system operating at an acceptablelevel.

SUMMARY

According to another implementation a method for treating wastewater mayinclude adding a magnesium compound to wastewater within a wastewatertreatment system. The method may also include adding an effective amountof a dispersing agent and a free magnesium control agent to wastewaterwithin the wastewater treatment system to control the formation ofstruvite scale within the wastewater treatment system.

One or more of the following features may be included. The method mayalso include measuring struvite scale formation within the wastewatertreatment system. The method may also include adjusting a concentrationof one or more of the dispersing agent and the free magnesium controlagent to reduce the struvite scale formation within the wastewatertreatment system. Adding the magnesium compound, and adding theeffective amount of the dispersing agent and the free magnesium controlagent may include adding an admixture including the magnesium compound,and the effective amount of the dispersing agent and the free magnesiumcontrol agent to wastewater within the wastewater treatment system. Themethod may include adding the magnesium compound to wastewater at afirst location within the wastewater treatment system. The method mayalso include adding the effective amount of the dispersing agent and thefree magnesium control agent to wastewater at a second location withinthe wastewater treatment system different from the first location.

The magnesium compound may include one or more of magnesium hydroxideand magnesium oxide. The magnesium hydroxide may exhibit an alkalinehydroxide purity of between about 85% to about 100%. The magnesiumhydroxide may also exhibit a caustic magnesia activity of between about50 seconds to about 1440 minutes. The magnesium hydroxide may alsoexhibit a particle size of between about 0.1 micron to about 50 microns.The magnesium hydroxide may also exhibit a specific surface area ofbetween about 9 m²/g to about 200 m²/g. The magnesium hydroxide mayfurther exhibit a stabilized residuals test value of between about 1milligram to about 50 grams. The magnesium oxide may exhibit an alkalinemagnesium oxide purity of between about 85% to about 100%. The magnesiumoxide may also exhibit a caustic magnesia activity of between about 50seconds to about 1000 seconds. The magnesium oxide may also exhibit aparticle size of between about 0.1 micron to about 30 microns. Themagnesium oxide may further exhibit a specific surface area of betweenabout 9 m²/g to about 300 m²/g.

The dispersing agent may include one or more of a polyacrylate, apolyamide, a polyacrylamide, a polyphosphate, a polyethylene glycolester, an ethoxylated alkyl phenol, an ethoxylated polyhydric alcohol,an ethoxylated polyhydric ether, and an ethoxylated polyhydric ester.The effective amount of the dispersing agent may include between about0.01% to about 90% of the dispersing agent relative to the weight of themagnesium compound. The admixture may include a slurry including betweenabout 0.01% to about 50% of the dispersing agent by weight of theslurry.

The free magnesium control agent may include one or more of a salt of apolyamine acetic acid, an acid of a polyamine acetic acid, an oxylate, apolyphosphonic acid, a polyphosphate, a gluconate, a carboxylatepolymer, and a polyaspartic acid. The effective amount of the freemagnesium control agent may include between about 0.01% to about 90% ofthe free magnesium control agent relative to the weight of the magnesiumcompound. The admixture may include a slurry including between about0.01% to about 50% of the free magnesium control agent by weight of theslurry.

According to another implementation a method for treating wastewater mayinclude adding a magnesium compound to wastewater within a wastewatertreatment system. The method may also include adding an effective amountof a dispersing agent and a seed material to wastewater within thewastewater treatment system to control the formation of struvite scalewithin the wastewater treatment system.

One or more of the following features may be included. The method mayinclude measuring struvite scale formation within the wastewatertreatment system. The method may also include adjusting a concentrationof one or more of the dispersing agent and the seed material to reducethe struvite scale formation within the wastewater treatment system.Adding the magnesium compound, and adding the effective amount of thedispersing agent and the seed material may include adding an admixtureincluding the magnesium compound, and the effective amount of thedispersing agent and the seed material to wastewater within thewastewater treatment system. The method may include adding the magnesiumcompound to wastewater at a first location within the wastewatertreatment system. The method may also include adding the effectiveamount of the dispersing agent and the seed material to wastewater at asecond location within the wastewater treatment system different fromthe first location.

The magnesium compound may include one or more of magnesium hydroxideand magnesium oxide. The magnesium hydroxide may exhibit an alkalinehydroxide purity of between about 85% to about 100%. The magnesiumhydroxide may also exhibit a caustic magnesia activity of between about50 seconds to about 1440 minutes. The magnesium hydroxide may alsoexhibit a particle size of between about 0.1 micron to about 50 microns.The magnesium hydroxide may also exhibit a specific surface area ofbetween about 9 m²/g to about 200 m²/g. The magnesium hydroxide mayfurther exhibit a stabilized residuals test value of between about 1milligram to about 50 grams. The magnesium oxide may exhibit an alkalinemagnesium oxide purity of between about 85% to about 100%. The magnesiumoxide may also exhibit a caustic magnesia activity of between about 50seconds to about 1000 seconds. The magnesium oxide may also exhibit aparticle size of between about 0.1 micron to about 30 microns. Themagnesium oxide may further exhibit a specific surface area of betweenabout 9 m²/g to about 300 m²/g.

The dispersing agent may include one or more of a polyacrylate, apolyamide, a polyacrylamide, a polyphosphate, a polyethylene glycolester, an ethoxylated alkyl phenols, an ethoxylated polyhydric alcohol,an ethoxylated polyhydric ether, and an ethoxylated polyhydric esters.The effective amount of dispersing agent may include between about 0.01%to about 90% of the dispersing agent relative to the weight of themagnesium compound. The admixture may include a slurry including betweenabout 0.01% to about 50% of the dispersing agent by weight of theslurry.

The seed material may include one or more of struvite seeds, amicro-silica, aluminum, iron, titanium, tin, copper, molybdenum,manganese, lanthanum, selenium, zeolites, clay, and volcanic ash. Theseed material may include a combination of micro-silica and aluminum.The seed material may include particles having a length of between about0.2 microns to about 1.0 millimeters. The effective amount of the seedmaterial may include between about 0.01% to about 90% of the seedmaterial relative to the weight of the magnesium compound. The admixturemay include a slurry including between about 0.01% to about 50% of theseed material includes by weight of the slurry.

According to another implementation, a method for treating wastewatermay include adding a magnesium compound to wastewater within awastewater treatment system. The method may also include adding aneffective amount of a dispersing agent to wastewater within thewastewater treatment system to control the formation of struvite scalewithin the wastewater treatment system.

One or more of the following features may be included. The method mayfurther include measuring struvite scale formation within the wastewatertreatment system. The method may also include adjusting a concentrationof the dispersing agent a to reduce the struvite scale formation withinthe wastewater treatment system. Adding the magnesium compound, andadding the effective amount of the dispersing agent may include addingan admixture including the magnesium compound and the effective amountof the dispersing agent to wastewater within the wastewater treatmentsystem.

The method may include adding the magnesium compound to wastewater at afirst location within the wastewater treatment system. The method mayalso include adding the effective amount of the dispersing agent at asecond location within the wastewater treatment system different fromthe first location. The second location may include an upstream locationrelative to the first location. The second location may include adownstream location relative to the first location. Adding the effectiveamount of the dispersing agent at the second location may includepre-conditioning the wastewater within the wastewater treatment systemto control the formation of struvite scale within the wastewatertreatment system. The method may further include adding one or more of afree magnesium control agent and a seed material at the second locationwithin the wastewater treatment system.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features andadvantages will become apparent from the description, the drawings, andthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts an example embodiment of a wastewatertreatment system.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

According to some implementations consistent with the present disclosurecompositions and methods for utilizing magnesium compounds in connectionwith various wastewater treatment processes and/or systems may beprovided while reducing or eliminating the occurrence of struviteaccumulation. For example, according to an embodiment, a method fortreating wastewater may include adding a magnesium compound towastewater within a wastewater treatment system.

In various embodiments, magnesium compounds may be utilized inconnection with wastewater treatment systems to improve the operationand/or efficiency of the wastewater treatment system, for example, byimproving wastewater collection and/or transport, improving one or morewastewater treatment processes, and/or by reducing necessary service ormaintenance of the wastewater treatment system. In some embodiments, themagnesium compound may include one or more of magnesium hydroxide,magnesium oxide, and/or magnesium hydroxide and/or magnesium oxidebearing compound.

For example, a magnesium hydroxide and/or magnesium oxide compound maybe added to wastewater within a wastewater treatment system to provideodor control within at least a portion of the wastewater treatmentsystem, thereby reducing or eliminating nuisance odors associated withthe wastewater treatment system. Further, in some embodiments, amagnesium compound, such as magnesium hydroxide and/or magnesium oxide,may be added to wastewater within a wastewater treatment system toreduce and/or control corrosion within the wastewater treatment system.For example, the magnesium compound may be utilized to control and/orreduce corrosion of pumping equipment (such as pump vanes and/or pumphousings) transport equipment (such as pipes, valves, valve bodies,debris grates, etc.), and/or processing equipment associated with thewastewater treatment system.

Magnesium compounds may also be added to wastewater within a wastewatertreatment system to provide an alkalinity source. For example, variousbiological processes, such as the biological reduction of ammonia (e.g.,nitrification) may produce various acids, such as nitric acid, nitrousacid, and carbonic acid. Magnesium compounds (e.g., magnesium hydroxideand/or magnesium oxide) may be added to wastewater within the wastewatertreatment system as source of alkalinity to stabilize the pH of theprocess. Similarly, magnesium compounds may be utilized in variousbiological treatment processes within a wastewater treatment system. Forexample, anaerobic digestion processes may generate acid. Magnesiumcompounds may be added to wastewater within a biological digestionprocess, and/or downstream from a biological digestion process, as analkaline source, which may improve the performance of the process,and/or mitigate effects associated with the acid production by thebiological digestion process.

Magnesium compounds may also be added to wastewater within a wastewatertreatment system to decrease and/or prevent the accumulation of fat,oil, and grease (e.g., “FOG”) within the wastewater treatment system,and/or to remove or decrease any FOG occlusions within at least aportion of the wastewater treatment system. FOG occlusions and/oraccumulations within a wastewater treatment system (e.g., withinconveyance pipes, pumps, valves, etc.,) may impede the flow ofwastewater through at least a portion of the wastewater treatmentsystem, and may, thereby, reduce the efficiency of the wastewatertreatment system. In some embodiments, adding magnesium compounds towastewater within a wastewater treatment system may reduce and/oreliminate FOG occlusions and/or accumulation.

In some embodiments, magnesium compounds may be added to wastewaterwithin a wastewater treatment system to eliminate, reduce, and/orcontrol the accumulation of gasses within wastewater and/or toeliminate, reduce, and/or control the emission of gasses from thewastewater. For example, wastewater within wastewater treatment systemsmay accumulate air and gasses, such as N₂, H₂S, NH₃, CO₂, NO_(x), O₂,and the like. Gas accumulation within wastewater may result from pumpingand transport of the wastewater, biological processes occurring withinthe wastewater treatment system (e.g., biological consumption and/ordecomposition of materials within the wastewater treatment system,etc.). Gas accumulation within and/or emission from the wastewatertreatment system may, for example, reduce operational efficiency of thewastewater treatment system by creating backpressure within wastewatertransport lines which must be overcome by upstream pumping equipment, bycreating suction head and/or cavitation within pumping systems, or thelike. Further, gas accumulation and/or emission may give rise tonuisance odors resulting from gas release around human populations, orthe like. In some embodiments, magnesium compounds may be added towastewater within a wastewater treatment system to prevent, control,and/or reduce the accumulation and/or emission of gases withinwastewater, for example, by facilitating one or more biologicalconsumption processes and/or decomposition processes, by preventing oneor more biological consumption processes and/or decomposition processesand/or through various additional and/or alternative mechanisms.

As will be appreciated, and as discussed herein, magnesium compounds,such as magnesium hydroxide and/or magnesium oxide, may be added towastewater within a wastewater treatment system to achieve variousdescribed and/or additional or alternative objectives. Further, it willbe appreciated that magnesium compounds may be added to wastewaterwithin a wastewater treatment system to achieve more than one objectiveand/or to influence more than one process and/or interaction occurringwithin a wastewater treatment system. Accordingly, it will be understoodthat any discussion regarding the addition of magnesium compounds towastewater within a wastewater treatment system is intended forillustrative purposes, and should not be construed as limiting thepresent disclosure. Further, some particular uses of magnesium compoundswithin wastewater treatment systems are described, for example, in U.S.patent application Ser. No. 13/853,465, entitled “Improving WastewaterPumping and Conveying Efficiency,” filed 29 Mar. 2013, which claims thebenefit of U.S. provisional patent application Ser. No. 61/618,336,filed on 30 Mar. 2012, the entire disclosure of both of which areincorporated herein by reference. Similarly, some particular uses ofmagnesium compounds within wastewater treatment systems are alsodescribed in U.S. patent application Ser. No. 13/613,963, entitled“Methods and Compositions for the Prevention of Struvite Scale Formationin Wastewater Systems,” filed 13 Sep. 2012, which claims the benefit ofU.S. provisional patent application Ser. No. 61/535,706, filed on 16Sep. 2011, the entire disclosure of both of which are also incorporatedherein by reference. Some particular example uses of magnesium compoundswithin wastewater treatment systems are also described in U.S. Pat. No.5,833,864, entitled “Method for the Reduction and Control of the Releaseof Gas and Odors from Sewage and Waste Water,” issued on 10 Nov. 1998,the entire disclosure of which is incorporated herein by reference.

The concentration of the magnesium compound added to the wastewatertreatment system may vary, for example, based on an intended objectivefor the magnesium compound. For example, as generally discussed above,magnesium compounds may be added to wastewater within a wastewatertreatment system to reduce corrosion of pumping equipment, conveyanceequipment, processing equipment or the like. Similarly, magnesiumcompounds may be added to wastewater within a wastewater treatmentsystem to facilitate treatment processes (e.g., biological processing oforganic materials, etc.) and/or control or mitigate by-products oftreatment processes (e.g., to increase the alkalinity and/or pH oftreated wastewater, etc.). Further, magnesium compounds may be utilizedto reduce and/or prevent the accumulation of FOG within a wastewatertreatment system and/or reduce or prevent the accumulation of gasseswithin wastewater. Magnesium compounds may be added to wastewater toachieve and/or facilitate various additional/alternative objectiveswithin a wastewater treatment system. Accordingly, it will beappreciated that the magnesium compound may be added to wastewaterwithin the wastewater treatment system at various concentrationsdepending upon the condition of the wastewater (e.g., pH, alkalinity,organic material content, etc.), an intended objective (increasingalkalinity, increasing pH, facilitating a treatment process, reducingFOG and/or gas entrainment, etc.) giving rise to the addition of themagnesium compound to the wastewater, a magnitude of change or impactthat may be desired, as well as various additional and/or alternativecriteria.

In some embodiments, magnesium compounds may be added to wastewaterwithin a wastewater treatment system to achieve a concentration ofbetween about 0.5 mg/L to about 10,000 mg/L in the wastewater. Forexample, in some embodiments, magnesium compounds may be added towastewater within a wastewater treatment system at a rate of betweenabout 5 mg/L to about 4,000 mg/L. In some embodiments, magnesiumcompounds may be added to wastewater within a wastewater treatmentsystem at a rate of between about 5 mg/L to about 1000 mg/L. Forexample, in an experiment embodiment, an effective concentration of amagnesium compound for reducing FOG and gas accumulation was in therange of between about 40 mg/L to about 105 mg/L. As discussed above,depending upon an intended usage and a condition of the wastewater,various concentrations of magnesium compounds may be utilized.Accordingly, the forgoing example concentration ranges should beunderstood as being for the purpose of illustration, and not oflimitation.

As discussed above, in some embodiments, the magnesium compound mayinclude magnesium hydroxide and/or magnesium oxide. Magnesium hydroxidemay be added to wastewater within a wastewater treatment system aseither a dry powder or as a slurry, e.g., which may include magnesiumhydroxide and/or magnesium oxide solids in water. In an illustrativeembodiment, magnesium hydroxide may be added to wastewater within awastewater treatment system as a slurry including between about 30% toabout 90% magnesium hydroxide solids in water. In one particularembodiment, magnesium hydroxide may be added to wastewater within awastewater treatment system as a slurry containing about 60% magnesiumhydroxide solids in water. Magnesium hydroxide slurries includingvarious additional/alternative solids content may suitably be utilized.Further, magnesium oxide may be added to wastewater within a wastewatertreatment system as a dry powder. Magnesium compounds may also be addedto wastewater including combinations of magnesium hydroxide andmagnesium oxide.

Magnesium oxide and/or magnesium hydroxide may be provided as variousnaturally occurring and/or synthetically produced and/or modifiedproducts. For example, magnesium oxide may be refined from naturallyoccurring magnesite that has been calcined to produce grades ofmagnesium oxide that may often be referred to as “caustic calcinedmagnesia.” Caustic calcined magnesia may be further hydrated to formmagnesium hydroxide. Magnesium hydroxide may also originate fromBrucite, which is a naturally occurring magnesium hydroxide deposit.Magnesium hydroxide from Brucite deposits may have a wide range ofpurity, which is often significantly lower in reactivity than causticcalcined magnesia products. Magnesium oxide and/or magnesium hydroxidecan be further produced as a precipitate from brine or seawater. Suchprecipitated magnesium oxide and/or magnesium hydroxide may often bereferred to as “synthetic magnesia,” which may often be provided havingreactivity characteristics that may be generally similar to causticcalcined magnesia varieties.

In some embodiments, magnesium compounds may be provided and utilizedthat may have characteristics which may exhibit increased suitabilityfor application in biological, near neutral and alkaline wastewatertreatment. For example, magnesium oxide and/or magnesium hydroxidecompounds may be provided having particular combinations of levels ofpurity, levels of stability, particle size and/or particle sizedistribution, specific surface area characteristics, and levels ofreactivity.

In an embodiment, magnesium compounds may be utilized having arelatively high degree of purity. In an example embodiment, magnesiumcompounds may be provided having an alkaline magnesium oxide and/oralkaline magnesium hydroxide purity of between about 85% to about 100%pure alkaline magnesium oxide and/or magnesium hydroxide. In anillustrative embodiment, a magnesium compound may be provided having analkaline magnesium oxide and/or alkaline magnesium hydroxide purity ofbetween about 91% to about 98% pure alkaline magnesium oxide and/ormagnesium hydroxide.

In some embodiments, the stability of the magnesium hydroxide may begenerally related to the ability of a magnesium hydroxide slurry tomaintain pumpability while minimizing solids residue that may accumulatein a storage and/or transportation tank (e.g., rail tank, tanker truck,etc.), which may become difficult to re-suspend. Accordingly, thestability of the magnesium hydroxide may be indicative of the ability ofa magnesium hydroxide slurry to withstand transportation and storage,while remaining susceptible to dispensing, as through pumping. In anexample embodiment, the stability of a magnesium hydroxide slurry may bequantified using the stabilized residuals test (“SRT-Tap Test”). Ingeneral, the SRT-Tap test may assess the solids settling stability ofmagnesium hydroxide suspensions. According to an embodiment, an eightfluid ounce test bottle may be filled with a magnesium hydroxide slurry.The magnesium hydroxide slurry may be retained in the test bottle for afourteen hour period, with the test bottle maintained in an uprightposition. After fourteen hours, sediment collecting in the bottom of thetest bottle (e.g., as a result of magnesium hydroxide falling out ofsuspension) may be evaluated. The test bottle containing the slurryand/or any collected sediment may be vigorously shaken in a horizontalorientation of the test bottle for fifteen seconds, and the slurry maythen be poured out of the test bottle. The test bottle may subsequentlybe filled with approximately an inch and a half of water, which may beswirled within the bottle to remove slurry film from the side of thebottle. The water may be poured from the test bottle and the test bottlemay be inverted to drain for fifteen minutes. A difference between thepost draining weight of the test bottle and an initial weight (e.g.,prior to initially filling the test bottle with magnesium hydroxideslurry) may be determined. According to various embodiments, a suitablemagnesium hydroxide may provide an SRT-Tap test value of between about 1milligram and about 50 gram. In some embodiments, a suitable magnesiumhydroxide may provide an SRT-Tap test value of between about 0.1 gram toabout 50 gram. In an embodiment, a suitable magnesium hydroxide mayprovide an SRT-Tap test value of between about 1 gram to about 50 gram.In an example embodiment, a suitable magnesium hydroxide may provide anSRT-Tap Test value of between about 1 gram and about 20 gram. In aparticular embodiment, a suitable magnesium hydroxide may provide anSRT-TAP Test value of between about 1 gram and about 20 grams, with anaverage value of about 10 grams.

In some embodiments, a magnesium compound may include magnesiumhydroxide exhibiting a caustic magnesia activity (“CMA”) neutralizationtime of between about 50 seconds to about 1440 minutes using 1.0N aceticacid and a magnesium hydroxide content of between about 10% to about100%. In some embodiments, a magnesium compound may include magnesiumoxide exhibiting a caustic magnesia activity neutralization time ofbetween about 50 seconds to about 1000 seconds using 1.0N acetic acidand a magnesium oxide content of between about 10% to about 100%. In anembodiment, the magnesium compound may be provided exhibiting a causticmagnesia activity neutralization time of between about 50 seconds toabout 200 seconds using a 1.0N acetic acid and a magnesium oxide and/ormagnesium hydroxide content of between about 10% to about 100%. In aparticular example embodiment, the magnesium compound may be providedexhibiting a caustic magnesia activity neutralization time of about 125seconds using a 1.0N acetic acid and a magnesium oxide and/or magnesiumhydroxide content of between about 10% to about 100%.

In an embodiment, the magnesium compound may be provided having aparticle size that may provide an enhanced specific surface area(“SSA”). For example, generally, a magnesium compound having a smallerparticle size may enhance the overall specific surface area of themagnesium compound (e.g., which may include magnesium oxide and/ormagnesium hydroxide). In an embodiment, a magnesium compound may includea magnesium hydroxide exhibiting a particle size of between about 0.1micron to about 50 micron. In some embodiments, a magnesium compound mayinclude magnesium oxide exhibiting a particle size of between about 0.1micron to about 30 micron. For example, in an embodiment, the magnesiumcompound may include a magnesium oxide and/or magnesium hydroxide havinga particle size of between about 1 micron to about 20 microns. In oneillustrative embodiment, the magnesium compound may include a magnesiumoxide and/or magnesium hydroxide having an average particle size ofabout 10 micron.

In addition to the average particle size, the magnesium compound may beprovided having a particle size distribution that may improve thestability of a slurry produced using the magnesium compound. Asgenerally discussed above, a higher degree of stability of a slurryproduced using the magnesium compound may generally relate to theability to maintain pumpability of the slurry while minimizing solidsresidue that may accumulate in a storage and/or transportation tank. Insome situations, a relatively more narrow particle size distribution ofthe magnesium compound may increase the stability of a slurry producedusing the magnesium compound. In an embodiment, particle size andparticle size distribution may be measured and/or controlled usingscreen analysis and a particle size distribution analyzer.

In an embodiment, a magnesium compound may be provided having a desiredreactivity. A magnesium compound having a relatively higher reactivitymay provide more complete and efficient use within a desiredapplication, and may, in some instances, at least partially offset arelatively low solubility that may be associated with magnesiumcompounds such as magnesium oxide and/or magnesium hydroxide. Forexample, a relatively higher reactivity may more efficiently facilitatebiological processes, increases in wastewater alkalinity, preventionand/or reduction of FOG and/or entrained gasses, etc., which may allowlower concentrations and/or amounts of magnesium compounds to beeffectively utilized. In an embodiment, specific surface area (“SSA”) ofthe magnesium compound may be correlated to reactivity, e.g., in which arelatively higher specific surface area may be correlated to arelatively higher reactivity. In some embodiments, a magnesium compoundmay include magnesium hydroxide exhibiting a specific surface area ofbetween about 9 m²/g to about 200 m²/g. For example, in an exampleembodiment, a magnesium compound may include magnesium hydroxide havinga specific surface area in the range of between about 9 m²/gram to about50 m²/gram. In one particular embodiment, a magnesium hydroxide mayinclude a specific surface area of about 12 m²/gram. In someembodiments, a magnesium compound may include magnesium oxide exhibitinga specific surface area of between about 9 m2/g to about 300 m2/g. Forexample, in an example embodiment, a magnesium compound may includemagnesium oxide having a specific surface area in the range of betweenabout 9 m²/gram to about 150 m²/gram. In a particular embodiment, amagnesium oxide may be provided having a specific surface area of about12 m²/gram.

Consistent with the foregoing, a magnesium compound may be added towastewater within a wastewater treatment system to achieve variousbeneficial effects. In an illustrative embodiment, the magnesiumcompound may include magnesium hydroxide having the attributes detailedin Table 1 below. The magnesium hydroxide may be provided as either apowder, and/or as a premixed slurry. In an embodiment in which themagnesium hydroxide may be provided as a premixed slurry, the slurry mayinclude between about 30% to about 90% magnesium hydroxide solids, withan average of 60% magnesium hydroxide solids, as indicated in the secondrow of Table 1.

TABLE 1 Attribute Property Avg Property Max Property Min MagnesiumHydroxide 60% 90% solids 30% solids Solids Purity of Magnesium 91-98%100% 85% Hydroxide CMA 125 secs 200 secs 50 secs Particle Size  10micron  20 micron  1 micron Stabilized Residuals Test  10 grams  20grams  1 milligram Specific Surface  12 m²/gram  50 m²/gram  9 m²/gramArea - SSA

In an illustrative embodiment, the magnesium compound may includemagnesium oxide having the attributes detailed in Table 2 below. Themagnesium oxide may be provided as a powder. In some embodiments, themagnesium oxide having the attributes detailed in Table 2 may be addeddirectly to wastewater within the wastewater treatment system (e.g., inpowder form) and/or may be mixed with water to provide a slurry, whichmay be added to wastewater within the wastewater treatment system.

TABLE 2 Attribute Property Avg Property Max Property Min Purity ofMagnesium 91-98% 100% 85% Oxide Specific Surface  12 m²/gram 150 m²/gram 9 m²/gram Area - SSA CMA 125 secs 200 secs 50 secs Particle Size  10micron  20 micron  1 micron

Consistent with the present disclosure, various components or additivesmay be utilized in connection with adding magnesium compounds towastewater within a wastewater treatment system. The components oradditives may prevent and/or reduce the occurrence of struvite scaleformation within at least a portion of the wastewater treatment system.For example, in an embodiment a method for treating wastewater within awastewater treatment system may also include adding an effective amountof a dispersing agent to wastewater within the wastewater treatmentsystem to control the formation of struvite within the wastewatertreatment system. In some embodiments, a method for treating wastewaterwithin a wastewater treatment system may also include adding aneffective amount of a dispersing agent and of one or more of a freemagnesium control agent and a seed material to wastewater within thewastewater treatment system to control the formation of struvite scalewithin the wastewater treatment system.

In general, struvite may include a mineral phosphate scale compound, andin particular, magnesium ammonium phosphate (e.g., which may also bereferred to ammonium magnesium phosphate). Struvite may, for example,include a relatively soft mineral having the chemical formulaNH₄MgPO₄-6H₂O, although other minerals may also be generally referred toas struvites. In some circumstances, struvite may form a scale onequipment within a wastewater treatment system that may, for example,damage equipment, clog wastewater conveyance pipes, or otherwise reducethe efficiency of operation of the wastewater treatment system. Forexample, struvite scale may form within wastewater transfer pipes,pumps, valves, mixer blades, tank walls, or the like.

While residential wastewater streams may often contain the components ofstruvite (e.g., Mg⁺², NH₄, and PO₄), the concentrations of theconstituents within the wastewater streams may often be insufficient toresult in the precipitation of struvite from the wastewater streams andthe formation of struvite scale within the wastewater treatment system.For example, in some circumstances, the availability of free magnesium(e.g., Mg⁺²) may limit the formation of struvite scale within awastewater treatment system. The addition of magnesium compounds torealize the above-discussed, and/or other, effects may increase theavailable free magnesium for the formation of struvite scale within thewastewater treatment system. Consistent with some embodiments,compositions and methods of the present disclosure may reduce and/oreliminate the formation and/or accumulation of struvite scale within awastewater treatment system. Further, in some embodiments, the presentdisclosure may reduce and/or eliminate the formation and/or accumulationof struvite scale within a wastewater treatment system to allow for theuse and/or addition of magnesium compounds within the wastewatertreatment system. As used herein, a wastewater treatment system maygenerally refer to one or more of a wastewater collection system, awastewater treatment facility or plant, and/or one or more individualtreatment processes within a wastewater treatment facility or plant.

As discussed above, a method for treating wastewater within a wastewatertreatment system may also include adding an effective amount of adispersing agent, alone, and/or in combination with one or more of afree magnesium control agent and a seed material to wastewater withinthe wastewater treatment system to control the formation of struvitescale within the wastewater treatment system. According to variousexample embodiments, adding a dispersing agent to wastewater within awastewater treatment system, alone, and/or in conjunction with one, orboth, of a free magnesium control agent and a seed material may reduceand/or eliminate the formation of struvite scale within at least aportion of the wastewater treatment system (e.g., within at least aportion of the wastewater treatment system adjacent to, and/ordownstream from, a location at which the dispersant and one, or both, ofthe free magnesium control agent and the seed material are added to thewastewater). It will be appreciated that while various embodimentsherein may describe and/or otherwise contemplate the use, inclusion,addition, etc., of a dispersing agent and one or more of a freemagnesium control agent and a seed material, further embodiments mayutilize a dispersing agent without the use of one or more of a freemagnesium control agent and a seed material. All such embodiments shouldbe considered as being contemplated by this disclosure. As such, anyfeatures, implementations, and alternatives described with respect toembodiments utilizing a dispersing agent and one or more of a freemagnesium control agent and a seed material should be construed as beingequally applicable to embodiments utilizing a dispersing agent withoutone or more of a free magnesium control agent and a seed material.

As generally used herein, a wastewater treatment system may include oneor more of a wastewater collection system, a wastewater treatmentfacility, and/or one or more individual processes or systems within awastewater treatment facility. With reference to FIG. 1, an examplewastewater treatment system is schematically depicted, including variouslocations and/or processes that may be subject to struvite scaleformation and/or collection. As discussed above, a magnesium compoundmay be added to a portion of the wastewater treatment system tofacilitate various processes (such as biological digestion of organicmaterial, etc.), to mitigate undesired circumstances or conditions(e.g., the production and/or release of odors, gasses, accumulation ofFOG, the occurrence of corrosion, and the like), and/or to otherwisefacilitate operation and/or efficiency of a wastewater treatment system.The addition of the magnesium compound may occur upstream in thewastewater treatment system relative to a region or location at whichthe action of the magnesium compound is desired. Similarly, the additionof the dispersing agent and either, or both, of the free magnesiumcontrol agent and the seed material may occur upstream in the wastewatertreatment system relative to a region or location at which the formationand/or collection of struvite scale may occur. Additionally a situationmay occur in which the formation and/or collection of struvite scale maytend to be the result of and/or accelerated by the addition of themagnesium compound to the wastewater. In such a situation, thedispersing agent and the one or more of the free magnesium control agentand/or the seed material may be added to the waste water at a locationthat may allow the effective amount of the dispersing agent and the oneor more of the free magnesium control agent and seed material to beachieved in a location of the wastewater treatment system that mayexperience the increased concentration of magnesium (e.g. which mayresult from the addition of the magnesium compound to the wastewater).

In the illustrated embodiment, wastewater may be received, collected andconveyed, by gravity and/or pumping at the wastewater collection system10. In an embodiment, wastewater collection system 10 may includevarious transport pipes, collection boxes, maintenance holes, pumpingstations, and the like. Wastewater collection system 10 may generallyreceive wastewater from various residential, commercial, and/orindustrial sources. The wastewater received by wastewater collectionsystem 10 may contain various quantities of organic materials, e.g.,that may be quantified by one or more of biological oxygen demand (BOD),chemical oxygen demand (COD), total suspended solids (TSS), ammonia(NH₃), dissolved oxygen (DO), nitrate (—NO₃), sulfate (—SO₄), and/orvarious chemical characteristics such as pH and alkalinity. Variousadditional and/or alternative chemical components may also be includedin wastewater received by wastewater collection system 10. In somesituations, wastewater collection system 10 may be a source of nuisanceodors, e.g., as a result of biological processes occurring within thewastewater and/or as a result of materials received from the variousresidential, commercial, and/or industrial sources. For example,nuisance odors may arise from H₂S gas, organic and/or inorganicphosphorus and/or nitrogen compounds (e.g., which may include —PO₄ ⁻³,—NO₃ ⁻¹, NH₄ ⁺¹, etc.). In some embodiments, magnesium compounds may beadded to wastewater within wastewater collection system 10 to mitigatesuch nuisance odors, as well as for other purposes (e.g., to reduce FOGaccumulation and/or occlusions, to reduce entrainment of gasses withinwastewater collection system 10, and/or to modify alkalinity, pH, and/orcorrosivity of the wastewater, or the like). Similarly, an effectiveamount of the dispersing agent and one or more of the free magnesiumcontrol agent and the seed material may be added to wastewater withinwastewater collection system 10 to control and/or reduce the formationand/or collection of struvite scale within wastewater collection system10 and/or downstream aspects of the wastewater treatment system.

The wastewater collected at wastewater collection system 10 may beconveyed to a wastewater processing system (e.g., wastewater processingsystem 12). Wastewater received from wastewater collection system 10 maybe received at headworks and preliminary treatment 14 of wastewaterprocessing system 12. Headworks and preliminary treatment 14 ofwastewater processing system 12 may provide, for example, removal ofgrit from the received waste water and preliminary screening. Headworksand preliminary treatment 14 may be a location within wastewaterprocessing system 12 that may be prone to significant corrosion andodors. In some situations, the significant odors and corrosion mayresult from turbulent conditions imparted on the wastewater withinheadworks and preliminary treatment 14. In some embodiments, magnesiumcompounds may be added to wastewater within, and/or upstream of,headworks and preliminary treatment 14, e.g., to mitigate odors and/orcorrosion within headworks and preliminary treatment 14, and/or forvarious additional and/or alternative purposes. Similarly, an effectiveamount of the dispersing agent and one or more of the free magnesiumcontrol agent and the seed material may be added to wastewater within,and/or upstream of, headworks and preliminary treatment 14 to controland/or reduce the formation and/or collection of struvite scale withinheadworks and preliminary treatment 14 and/or downstream aspects of thewastewater treatment system.

Primary treatment/clarification 16 may generally provide the firstprocess within wastewater processing system 12 in which solids and watermay diverge to follow separate treatment trains. In the exampleembodiment of FIG. 1, the diverging water and solids treatment trainsmay undergo various processes. For example, wastewater enteringwastewater processing system 12 may be conveyed from primarytreatment/clarification 16 to biological treatment 18, which may also bereferred to as secondary treatment, whether the processing utilizesconventional active sludge (AS), sequential batch reactors (SBR),biological nutrient removal (BNR), enhanced nutrient removal (ENR),enhanced biological phosphorus removal (EBPR) or other processing.Processing within biological treatment 18 may include aerobic, anoxic,or anaerobic, as well as combinations thereof, which may variouslyfacilitate removal and/or separation of organic materials, and/orconstituents. Wastewater from biological treatment 18 may be conveyed tosecondary/final clarification 20, where biosolids may be separated fromthe wastewater and may be transferred to a solids treatment train.Following secondary/final clarification 20, the waste water may undergodisinfection 22 and final effluent 24, e.g., which may include optionalpH adjustment.

In the illustrative example of FIG. 1, a solids treatment train maytreat solids that enter wastewater processing system 12, either directlyand/or biosolids that may be generated within wastewater processingsystem 12 (e.g., via secondary/final clarification 20). For example,solids may undergo digestion 26, which may include aerobic and/oranaerobic processing. In some embodiments, digestion 26 may be precededby a solids thickening process. The digested solids may undergo storageand/or post digestion 28. Solids transfer 30 may proceed from digestion26 to and thru storage and dewatering. The solids accumulated, produced,and treated within wastewater processing system 12 may undergodewatering 32 (e.g., via drying beds, filter presses, or centrifuge).

As generally described with respect to FIG. 1, a wastewater treatmentsystem may include various collection, treatment, or processingoperations. At least some of the collection and/or treatment operationsmay be facilitated by, and/or potential associated problems, drawbacks,or issues with such operations may be reduced and/or controlled throughthe addition of magnesium compounds to wastewater within the wastewatertreatment system. In some situations, wastewater within the wastewatertreatment system may contain the constituents for forming struvite,namely Mg⁺², NH₄ ⁺, and PO₄ ⁻³. Further, in some circumstances, addingmagnesium compounds to wastewater within the wastewater treatment systemmay further contribute Mg⁺² constituents to the wastewater, which mayresult in, and/or accelerate or increase, the potential for theformation and/or collection of struvite scale within at least portionsof the wastewater treatment system. Industrial wastewater, which may becollected and/or processed by the wastewater treatment system, maycontain relatively high levels of phosphate, ammonia, and/or elevatedpH, which may in some circumstances cause, or increase, the potentialfor the formation and/or collection of struvite scale within at leastportions of the wastewater treatment system.

Consistent with some embodiments, the addition of an effective amount ofa dispersing agent, alone and/or in conjunction with one or more of afree magnesium control agent and a seed material, may reduce and/orcontrol the formation and/or collection of struvite scale within atleast a portion of the wastewater treatment system. In an examplesituation, the addition of the effective amount of the dispersing agentand one or more of the free magnesium control agent and the seedmaterial may reduce the potential for the formation of struvite scalewithin at least a portion of the wastewater treatment system.

In an example wastewater treatment system, such as shown in FIG. 1, thepotential for struvite formation and/or collection may be relativelygreater in anaerobic digesters, sludge storage and/or sludge dewateringprocesses and/or related equipment. For example, the potential forstruvite scale formation and/or collection may be relatively greater intransfer pipelines, pumps, valves, mixer blades, tank walls, and thelike. In some situations, the potential for struvite formation and/orcollection may be relatively greater as a result of turbulence triggersand/or localized pH conditions that may facilitate struvite formationand/or collection. For example, the potential for struvite scaleformation and/or collection may be relatively higher in belt filterpresses, filtrate lines, digesters, digested sludge, holding tanks,sludge transport lines, pumps and valves. In such locations and/orprocesses the necessary constituents of struvite (e.g., Mg⁺², NH₄ ⁺, andPO₄ ⁻³) may be relatively higher, and consequently, small changes in pHmay trigger substantial struvite formation. Accordingly, in someembodiments, the effective amount of the dispersing agent and one ormore of the free magnesium control agent and the seed material may beadded to, and/or upstream relative to, the collection system, ananaerobic digester, a storage tank or process, a dewatering processand/or side stream biological systems downstream of an anaerobicdigester.

Consistent with the foregoing description, in an embodiment, one or moreof the magnesium compound and the effective amount of the dispersingagent and one or more of the free magnesium control agent and the seedmaterial may be added to wastewater within a wastewater collectionsystem. In some embodiments, one or more of the magnesium compound andthe effective amount of the dispersing agent and one or more of the freemagnesium control agent and the seed material may be added to wastewaterwithin a wastewater treatment process (e.g., which may include awastewater treatment facility or plant, and/or an individual wastewatertreatment process within a wastewater treatment facility or plant).Further, one or more of the magnesium compound and the effective amountof the dispersing agent and one or more of the free magnesium controlagent and the seed material may be added to wastewater within awastewater collection system and one or more of the magnesium compoundand the effective amount of the dispersing agent and one or more of thefree magnesium control agent and the seed material may be added towastewater within a wastewater treatment process (e.g., which mayinclude a wastewater treatment facility or plant, and/or an individualwastewater treatment process within a wastewater treatment facility orplant).

As generally discussed above, adding the magnesium compound towastewater within a wastewater treatment system may include adding themagnesium compound to wastewater at, and/or upstream, of a location ofthe wastewater treatment system at which the action of the magnesiumcompound (e.g., corrosion prevention, odor reduction, etc.) is desired.Similarly, adding the effective amount of the dispersing agent and theone or more of the free magnesium control agent and the seed materialmay include adding the effective amount of the dispersing agent and theone or more of the free magnesium control agent and the seed materialat, and/or upstream, of a location at which struvite scale controland/or reduction is desired. In some embodiments, the magnesium compoundand the effective amount of the dispersing agent and the one or more ofthe free magnesium control agent and the seed material may be added atthe same location within the wastewater treatment system. In suchembodiments, the magnesium compound and the dispersing agent, aloneand/or in conjunction with one or more of a free magnesium control agentand a seed material, may be added together, for example as separatecomponents added at a common location, as an admixture added at alocation, and/or as various individual components and admixtures ofindividual components added at a common location. In some embodiments,the magnesium compound and the effective amount of the dispersing agentand the one or more of the free magnesium control agent and the seedmaterial may be added to wastewater within the wastewater treatmentsystem at different locations. In such embodiments, the magnesiumcompound and the dispersing agent, alone and/or in conjunction with oneor more of a free magnesium control agent and a seed material may beadded to wastewater within the wastewater treatment system at differentlocations as individual components and/or as admixtures of individualcomponents. For example, an admixture of the magnesium compound and thedispersing agent may be added at one location and an admixture of a freemagnesium control agent and a seed material may be added at anotherlocation. In a similar embodiment, the magnesium compound may be addedat one location, and admixture of a dispersing agent and a freemagnesium control agent may be added at another location, and a seedmaterial may be added at the same location as the magnesium compound, atthe same location as the admixture of the dispersing agent and the freemagnesium control agent, and/or at a different location. Variousadditional/alternative embodiments may be equally utilized.

In an embodiment, a method may include adding the magnesium compound towastewater at a first location within the wastewater treatment system.The method may also include adding the effective amount of thedispersing agent, along and/or in conjunction with the one or more ofthe free magnesium control agent and the seed material, to wastewater ata second location within the wastewater treatment system different fromthe first location. The second location may be either upstream ordownstream from the first location. For example, in some embodiments,the effective amount of the dispersing agent and the one or more of thefree magnesium control agent and the seed material may be added near,and/or upstream from, a location within the wastewater treatment systemhaving a relatively higher potential for the formation and/or collectionof struvite scale. In some embodiments, the dispersing agent, aloneand/or in conjunction with one or more of the free magnesium controlagent and the seed material, may be added at the second location whichmay be upstream of the first location (i.e., the location at which themagnesium compound may be added to the wastewater treatment system). Insuch an embodiment, the dispersing agent (alone and/or in conjunctionwith one or more of the free magnesium control agent and the seedmaterial) may precondition the wastewater. In an embodiment,preconditioning the wastewater may reduce the likelihood and/oroccurrence of struvite scale formation upon the addition of themagnesium compound at the first location (e.g., which may be downstreamfrom the second location). The effective amount of the dispersing agentand the one or more of the free magnesium control agent and the seedmaterial may be added to wastewater within the wastewater treatmentsystem at the same location as one another. In some embodiments, each ofthe effective amount of the dispersing agent and the one or more of thefree magnesium control agent and the seed material may be added towastewater within the wastewater treatment system at different locationsfrom one another.

As generally described above, in some embodiments the magnesium compoundand one or more of the effective amount of the dispersing agent and theat least one of the free magnesium control agent and the seed materialmay be added to wastewater at a generally common location within thewastewater treatment. In such an embodiment, the effective amount of thedispersing agent and at least one of the free magnesium control agentand the seed material may be present in the same flow of wastewater asthe added magnesium compound. In some embodiments, adding the magnesiumcompound, and adding the effective amount of the dispersing agent andthe one or more of the free magnesium control agent and the seedmaterial may include adding an admixture including the magnesiumcompound, and the effective amount of the dispersing agent, and the oneor more of the free magnesium control agent and the seed material towastewater within the wastewater treatment system. As also discussed, insome embodiments the magnesium compound may be added to wastewaterwithin the wastewater treatment system separately from the effectiveamount of the dispersing agent and the one or more of the free magnesiumcontrol agent and the seed material. In various embodiments, theeffective amount of the dispersing agent and the one or more of the freemagnesium control agent and the seed material may be separately added towastewater within the wastewater treatment system, and/or may be addedto wastewater within the wastewater treatment system as an admixture.

In an embodiment, a method for controlling the formation and/orcollection of struvite scale within a wastewater treatment system mayinclude measuring struvite scale formation within the wastewatertreatment system. Measuring struvite scale formation within thewastewater treatment system may include, for example, visuallyinspecting at least a portion of the wastewater treatment system for thepresence of struvite scale. Further, measuring struvite scale formationwithin at least a portion of the wastewater treatment system may alsoinclude determining a quantitative and/or qualitative relative amount ofstruvite scale formation within the portion of the wastewater treatmentsystem. As generally discussed above, in some circumstances, struvitescale formation and/or collection may tend to occur, e.g., in transferpipelines, pumps, valves, mixer blades, tank walls, belt filter presses,filtrate lines, digesters, digested sludge, and the like. Measuringstruvite scale formation may include visually inspecting one or more ofsuch locations for the presence and/or relative quantity of struvitescale formation and/or collection.

In addition/as an alternative to visual inspections, other techniquesmay also be utilized for measuring struvite scale formation. Forexample, struvite scale formation may be inferred and/or measured basedon a decrease in performance and/or efficiency within the wastewatertreatment system, such as a decrease in pump efficiency, pipelinethroughput, valve operation, etc., which may be the result of struvitescale formation. In another example, struvite scale formation may bemeasured based on, e.g., a chemical analysis of wastewater within atleast a portion of the wastewater treatment system. For example, adecrease in the constituents of struvite (e.g., Mg⁺², NH₄ ⁺, and PO₄ ⁻³)may be indicative of struvite formation. For example, the formation ofstruvite within the wastewater treatment system may result in a decreasein constituents of struvite in wastewater flows downstream from thelocation of the struvite formation. Various additional and/oralternative methods may be utilized for measuring the formation ofstruvite within the wastewater treatment system.

Based upon, at least in part, measurements of the formation of struvitewithin at least a portion of the wastewater treatment system, aconcentration of one or more of the dispersing agent and the one or moreof the free magnesium control agent and the seed material may beadjusted. For example, in the event that measuring the formation ofstruvite indicates that undesirable amounts of struvite are formingand/or collecting within at least a portion of the wastewater treatmentsystem, the concentration of one or more of the dispersing agent and theone or more of the free magnesium control agent and the seed materialmay be adjusted, e.g., to reduce struvite formation within thewastewater treatment system. In some embodiments, the quantity of one ormore of the dispersing agent and the one or more of the free magnesiumcontrol agent and the seed material may serve as a proxy for theconcentration of the added dispersing agent, free magnesium controlagent, and/or the seed material.

As discussed above, the concentration of one or more of the dispersingagent and the one or more of the free magnesium control agent and theseed material may be adjusted to reduce the formation of struvite scalewithin the wastewater treatment system. The concentration of one or moreof the dispersing agent and the one or more of the free magnesiumcontrol agent and the seed material may be adjusted to achieve a desiredlevel of struvite reduction efficiency. For example, completelyeliminating struvite scale formation from within at least a portion ofthe wastewater treatment system requires a relatively large (e.g., andtherefore costly) amount of the dispersing agent and one or more of thefree magnesium control agent and the seed material. Further, in somesituations, the complete elimination of struvite may not be possible.Further, some level of struvite formation may be acceptable, forexample, as not unduly compromising the efficiency and/or operation ofthe wastewater treatment system. Accordingly, adjusting theconcentration of the dispersing agent and the one or more of the freemagnesium control agent and the seed material may include increasingand/or decreasing the concentration of the dispersing agent and the oneor more of the free magnesium control agent and the seed material toachieve a desired balance between reduction of struvite scale within atleast a portion of the wastewater treatment system and the cost ofachieving a further reduction of struvite scale within the wastewatertreatment system.

Consistent with the foregoing, a magnesium compound may be added towastewater within a wastewater treatment system to facilitate variousprocesses and/or to reduce or eliminate potential sources ofinefficiencies (e.g., FOG accumulation, gas entrainment withinwastewater, etc.), and/or eliminate potential undesirable circumstances(e.g., corrosion, nuisance odors, undesirable alkalinity or pHconditions, etc.), and/or to achieve other effects. In some embodiments,the magnesium compound may be added to the wastewater as a slurry and/oras a powder. Further, as discussed above an effective amount of adispersing agent and one or more of a free magnesium control agent and aseed material may be added to wastewater within a wastewater treatmentsystem to control struvite scale formation and/or collection. In someembodiments, the dispersing agent, the free magnesium control agent,and/or the seed material may be added to wastewater within thewastewater treatment system along with the magnesium compound. In anembodiment, an admixture including the magnesium compound and aneffective amount of the dispersing agent and the one or more of the freemagnesium control agent and the seed material may be added to wastewaterwithin the wastewater treatment system. In various embodiments, theadmixture including the magnesium compound, the dispersing agent, andthe one or more of the free magnesium control agent and the seedmaterial may be provided as a slurry, as a power, and/or may otherwisebe provided.

In some embodiments, one or more of the dispersing agent, the freemagnesium control agent, and the seed material may be added towastewater within the wastewater treatment system separately from themagnesium compound. In an embodiment, an admixture including thedispersing agent and the one or more of the free magnesium control agentand the seed material may be added to wastewater within the wastewatertreatment system separately from the magnesium compound. In variousembodiments, the admixture of the dispersing agent and the one or moreof the free magnesium control agent and the seed material may beprovided as a slurry, a powder, and/or otherwise provided.

A dispersing agent may include an agent that may, at least in part,facilitate maintaining at least a portion of a the magnesium compoundadded to wastewater within the wastewater treatment system dispersedtherein, so as to reduce precipitation of the magnesium compound.Further, keeping at least a portion of the magnesium compound dispersedmay reduce and/or prevent reaction of the magnesium compound withammonia and/or phosphate to form struvite scale. The dispersing agentmay include, for example, a nonionic, a cationic, and/or an amphotericsurfactant, as well as combinations thereof. The dispersing agent mayinclude, but is not limited to, one or more of a polyacrylate, apolyamide, a polyacrylamide, a polyphosphate, a polyethylene glycolester, an ethoxylated alkyl phenol, an ethoxylated polyhydric alcohol,an ethoxylated polyhydric ether, and an ethoxylated polyhydric ester,and others such as polycarboxylates, polymaleic acids, and polymaleicanhydrides.

In an example embodiment, a suitable dispersing agent may be based on apolymeric acrylate, such as supplied under the trade name of Flosperse™by SNF Inc. In some embodiments, enhanced and/or synergistic effects maybe realized by combining certain dispersing agents. For example, asystem of dispersing agents may be achieved including a polyacrylateblended with an ethoxylated polyhydric alcohol. In a particular case,such a dispersing agent system may be beneficial in circumstances inwhich FOG accumulation may exist within the wastewater treatment system.The enhanced effects of using such a system of dispersing agents in thepresence of FOG may be based on, at least in part,Hydrophilic/Lipophilic Balance (HLB) requirements.

According to various embodiments, one or more dispersing agents may beadded to wastewater within the wastewater treatment system in a range ofapproximately 0.1 mg/L to approximately 200 mg/L. In an illustrativeembodiment, the one or more dispersing agents may be added to wastewaterwithin a wastewater treatment system in an amount of between about 2.0mg/L to about 6.0 mg/L. As generally discussed above, the one or moredispersing agents may be added directly to the wastewater within thewastewater treatment system, and/or may be combined in an admixture withat least the magnesium compound. In an embodiment in which thedispersing agent may be combined in an admixture with the magnesiumcompound, the admixture may include between about 0.01% to about 90% ofthe dispersing agent relative to the weight of the magnesium compound.Further, a slurry admixture may include between about 0.01% to about 50%of the dispersing agent by weight of the slurry. It will be appreciatedthat the exact amount of the dispersing agent may be selected and/orvaried to achieve a desired reduction in struvite scale formation withinthe wastewater treatment system. As such, the illustrative ranges shouldbe construed as illustrative and not as a limitation. Further, while notspecifically described various additional ranges, within the describeddosage ranges, may also be utilized.

An illustrative example of slurry admixture formulation including amagnesium compound and utilizing a polyacrylate as a dispersing agent isdetailed below in Table 3. Various additional/alternative admixtures maybe provided consistent with the present disclosure.

TABLE 3 % Concentration (based Component on wt./wt. basis) Magnesiumhydroxide 53.2% Polyacrylate Dispersant  2.3% (50% active) Water(distilled) 44.5%

As generally discussed above, in some situations the availability ofMg⁺² within the wastewater may be a limiting factor on the formation ofstruvite scale. In some embodiments, the free magnesium control agentmay be effective in reducing and/or restricting the availability of Mg⁺²within the wastewater for reacting with free phosphorous or nitrogen.For example, in an embodiment the free magnesium control agent maychemically react with free magnesium ions (e.g., which may be presentin, or provided by an added magnesium compound, such as an Mg(OH)₂slurry; and/or may be otherwise present in the wastewater), and maythereby prevent such magnesium ions from reacting with free phosphorousor nitrogen ions. In some embodiments, the free magnesium control agentmay either sequester or chelate free magnesium and prevent and/or reducethe formation of struvite.

As discussed above, in some embodiments, the free magnesium controlagent may include a sequestering agent and/or a chelating agent. Forexample, the free magnesium control agent may include, but is notlimited to, one or more of a salt of a polyamine acetic acid, an acid ofa polyamine acetic acid (e.g., ethylene diamine tetraacetic acid (EDTA),nitrilotriacetic acid (NTA), cyclohexane diamine acetic acid (CDTA),diethylyene triamine pentaacetic acid (DTPA)), an oxylate (e.g., sodiumoxylate), a polyphosphonic acid, a polyphosphate (e.g., sodiumtetrasodiumpryophosphate (TSPP), hexametaphosphate (SHMP) and others), agluconate (e.g., sodium gluconates), a carboxylate polymer, and apolyaspartic acid, as well as other chemicals that may have chelationproperties to magnesium, phosphate and/or ammonium. In general, manyvarieties of chelants and/or sequestrants may be utilized as freemagnesium control agents to reduce and/or prevent the formation ofstruvite within at least a portion of a wastewater treatment system. Inan example embodiment, the free magnesium control agent may include asalt and/or an acid of ethylene diamine tetraacetic acid.

According to various embodiments, one or more free magnesium controlagents may be added to wastewater within a wastewater treatment systemat a dosage of between about 0.01 mg/L to about 200 mg/L of the systemto be treated. In a particular illustrative embodiment, one or more freemagnesium control agents may be added to wastewater within a wastewatertreatment system at a dosage of between about 0.1 mg/L to about 6.0 mg/Lof the system to be treated. Consistent with the foregoing description,in some embodiments the free magnesium control agent may be addeddirectly to wastewater within the wastewater treatment system, and/ormay be combined in an admixture with at least the magnesium compound. Inan embodiment in which the free magnesium control agent is combined inan admixture with the magnesium compound, the admixture may includebetween about 0.01% to about 90% of the free magnesium control agentrelative to the weight of the magnesium compound. Further, in anembodiment in which the magnesium compound may be provided as a slurry,a slurry admixture may include between about 0.01% to about 50% of thefree magnesium control agent by weight of the slurry. It will beappreciated that the exact amount of the free magnesium control agentmay be selected and/or varied to achieve a desired reduction in struvitescale formation within the wastewater treatment system. As such, theillustrative ranges should be construed as illustrative and not as alimitation. Further, while not specifically described various additionalranges, within the described dosage ranges, may also be utilized.

An illustrative example of a slurry admixture including a magnesiumcompound and utilizing diethylene triamine pentaacetic acid (DPTA) as afree magnesium control agent is detailed below in Table 4. Variousadditional/alternative admixtures may be provided consistent with thepresent disclosure.

TABLE 4 % Concentration (based Component on a wt./wt. basis) MagnesiumHydroxide 52.0% Diethylyene triamine pentaacetic  9.8% acid (DTPA) Water(distilled) 38.2%

In some embodiments, seed materials may be added to wastewater within awastewater treatment system, at least in part, to reduce and/or assistin reducing the formation of struvite scale within at least a portion ofthe wastewater treatment system. In some situations, the seed materialadded to wastewater having the potential for struvite formation (e.g.,wastewater that may contain Mg⁺², NH₄ ⁺, and PO₄ ⁻³) may act as anattractant for one or more of free magnesium, free ammonium, and/or freephosphate compounds within the wastewater. As discussed above, one ormore of the free magnesium, free ammonium, and/or free phosphatecompounds may be the result of additions to the wastewater (e.g., in theform of added magnesium compounds and/or added ammonium or phosphatecompounds) and/or may result from various treatment processes and/ordecomposition of materials within the wastewater. In some embodiments,the seed material may attract struvite to form on the surface of theseed material, and may grow in size (e.g., due to the accumulation ofstruvite) while staying dispersed in the wastewater. To the extent thatthe seed material (including any accumulated struvite thereon) mayremain dispersed in the wastewater (e.g. and not fall out ofsuspension), the seed material may prevent and/or reduce the formationof struvite scale building upon on metallic, plastic, and/or concretesurfaces, which may lead to occlusion and/or impairment of free flowingwastewater through at least the affected portions of the wastewatertreatment system. In this regard, in some embodiments, struvite scalemay preferentially form and/or accumulate on the seed material and,therefore, remain dispersed in the wastewater.

The seed material may include a material in the form of small crystals.For example, the seed material may include particles and/or crystalshaving a length of between about 0.2 microns to about 1.0 millimeters.In an embodiment, the seed material may include particles and/orcrystals having a length of between about 2.0 microns to about 0.1millimeters. Examples of suitable seed materials may include, but arenot limited to, one or more of struvite seeds (e.g., as described inU.S. patent application Ser. No. 13/613,963, entitled “Methods andCompositions for the prevention of Struvite Scale Formation inWastewater Systems,” filed on 13 Sep. 2012, which claims the benefit ofU.S. provisional patent application Ser. No. 61/535,706, filed on 16Sep. 2011, the entire disclosures of both of which are incorporatedherein by reference), a micro-silica, aluminum; iron, titanium, tin,copper, molybdenum, manganese, lanthanum, selenium, a zeolite, clay, andvolcanic ash, as well as other materials that have an affinity forstruvite components (i.e., magnesium, phosphate and ammonium). Amicro-silica may include, for example, one or more of a silica fume, afumed silica, and a colloidal silica. In some embodiments, the seedmaterials may be based on micro-silicas and/or metals. Further, in someinstances synergistic combinations of seed materials may be realized inthe form of blends of micro-silicas with metals. In one exampleembodiment, the seed material may include a combination of micro-silicaand aluminum. The composition of the seed material and/or combination ofseed materials may be based on, at least in part, the actual conditionswithin the wastewater treatment system. For example, in a situation inwhich an excess of phosphate is present within the wastewater, the useof a combination of aluminum and lanthanum seed materials may provideadvantageous results, e.g., by attracting free phosphate compounds.

According to various embodiments, one or more seed materials may beadded to wastewater within the wastewater treatment system in a dosagerange of between about 0.1 mg/L to about 200 mg/L into the system to betreated. In a particular illustrative embodiment, one or more seedmaterials may be added to wastewater within the wastewater treatmentsystem at a dosage of between about 2.0 mg/L to about 6.0 mg/L in thesystem to be treated. As generally discussed above, the one or more seedmaterials may be added directly to the wastewater within the wastewatertreatment system and/or may be combined in an admixture with at leastthe magnesium compound. In an embodiment in which the seed material iscombined in an admixture with the magnesium compound, the admixture mayinclude between about 0.01% to about 90% of the seed material relativeto the weight of the magnesium compound. The admixture may include, forexample, a dry admixture, a slurry, and/or another admixture. In anembodiment in which the admixture may include a slurry, the slurryadmixture may include between about 0.001% to about 50% of the seedmaterial includes by weight of the slurry.

An illustrative example of a slurry admixture including magnesiumhydroxide and fumed silica as a seed material is detailed below in Table5. Various additional and/or alternative admixtures may be providedconsistent with the present disclosure.

TABLE 5 % Concentration (based Component on a wt./wt. basis) MagnesiumHydroxide 55.0% Fumed Silica  1.6% Water (distilled) 43.4%

In some embodiments, which may be based on, at least in part, particularchemistries and/or conditions of the wastewater within at least aportion of the wastewater treatment system, synergistic effects forreducing and/or preventing the formation and/or accumulation of struvitescale within at least a portion of the wastewater treatment system maybe achieved through particular combinations of dispersing agents andseed materials, particular combinations of dispersing agents and freemagnesium control agents. Further advantageous combinations ofparticular dispersing agents, with particular free magnesium controlagents, and particular seed materials may also be realized. The relativelevels, or concentration, of each component may depend, at least inpart, on the desired effect and the nature of the components. Suchcombinations of components, added directly to wastewater within thewastewater treatment system and/or utilized in an admixture with amagnesium compound, such as in a magnesium hydroxide slurry, may providecost effective control and/or reduction of struvite scale withinportions of the wastewater treatment system, such as collectionssystems, aerobic and/or anaerobic digesters, transition areas, and thelike.

In an illustrative embodiment, a slurry admixture may include magnesiumhydroxide in combination with a polyacrylate dispersing agent, anethylene diamine tetraacetic acid sequestering agent (e.g., freemagnesium control agent), and a silica fume seed material. Each of thedispersing agent, the free magnesium control agent, and the seedmaterial may be provided at between about 0.01% to about 10.0% based onthe weight of the magnesium hydroxide. Further admixtures, for example,include various combinations of dispersing agents, free magnesiumcontrol agents, and seed materials. In some embodiments, the selectedcomponents may be added to wastewater within the wastewater treatmentsystem at dosages of between about 0.01 mg/L to about 500 mg/L into thesystem to be treated. In a particular illustrative embodiment, thecombined selected components may be added to wastewater within thewastewater treatment system at a dosage of between about 0.01 mg/L toabout 50.0 mg/L in the system to be treated. In an illustrativeembodiment in which the combined components may be combined in admixturewith a magnesium compound slurry, the combined selected components mayinclude between about 0.01% to about 50% by weight of the slurry.

A slurry admixture may include a scale reducer. For example, a scalereducer may assist in removing at least a portion of any pre-existingstruvite scale that may have accumulated within at least a portion ofthe wastewater treatment system. Further, a scale reducer may assist inremoving at least a portion any struvite scale that forms within atleast a portion of the wastewater treatment system (e.g., whichformation may be at least partially reduced consistent with the presentdisclosure). In an embodiment, the scale reducer may include one or moreof ascorbic acid, citric acid, acetic acid, and an organic derivative ofone or more of ascorbic acid, citric acid, acetic acid, and an alkylamine acetic acid. In some embodiments, the scale reducing may includean inorganic acid, such as hydrochloric acid, sulfuric acid, as well asother inorganic acids. The scale reducing agent may be added towastewater within the wastewater treatment system at a dosage of betweenabout 0.1 mg/L to about 200 mg/L into the system to be treated. In anillustrative embodiment, the scale reducing agent may be added towastewater within the wastewater treatment system at a dosage of betweenabout 2.0 mg/L to about 6.0 mg/L in the system to be treated. In asimilar manner to the dispersing agent, the free magnesium controlagent, and/or the seed material, the scale reducing agent may be addeddirectly to the wastewater within the wastewater treatment system.Further, the scale reducing agent may be combined in an admixture withone or more other components. For example, the scale reducing agent maybe combined in an admixture including at least the magnesium compound.As described above, an admixture include the magnesium compound mayinclude a slurry. According to an illustrative embodiment, the slurryadmixture may include between about 0.01% to about 50% of the scalereducer by weight of the slurry.

In an illustrative example, a scale reducing agent may be used incombination with one or more struvite scale reducing additives, such asa dispersing agent and one or more of a free magnesium control agent anda seed material. In such a combination, the scale reducing agent may beadded to wastewater within the wastewater treatment system at a dosageof between about 0.1 mg/L to about 1.0 g/L into the system to betreated. In one particular illustrative embodiment, a scale reducingagent included in combination with one or more struvite scale reducingadditives may be added to wastewater within a wastewater treatmentsystem at a dosage of between about 2.0 mg/L to about 500 mg/L in thesystem to be treated. The combination of the scale reducing agent andthe struvite scale reducing additives may be added directly towastewater within the wastewater treatment system, and/or may becombined in admixture with a magnesium compound. In one embodiment inwhich the combination of the scale reducing agent and the one or morescale reducing additives are combined in admixture with a magnesiumcompound, the admixture may include a magnesium hydroxide slurry, andthe concentration of the combined scale reducing agent and the one ormore scale reducing additives maybe provided at between out 0.01% toabout 50% by weight of the slurry.

An example of an embodiment of a slurry admixture including magnesiumhydroxide as a magnesium compound, ethylene diamine tetraacidic acid(EDTA) as a free magnesium control agent, polyacrylamide as a dispersingagent, silica fume as a seed material, and ascorbic acid as a scalereducing agent is detailed below in Table 6. Variousadditional/alternative admixtures may be provided consistent with thepresent disclosure.

TABLE 6 % Concentration (based Component on a wt./wt. basis) MagnesiumHydroxide 50.4% Ethylene diamine tetraacidic  2.7% acid (EDTA)Polyacrylamide Dispersant  1.5% (60% active) Silica Fume Seed  0.5%Ascorbic Acid  1.1% Water 43.8%

Consistent with the foregoing description, magnesium compounds, such asmagnesium oxide and magnesium hydroxide, may be used in variousapplications in wastewater treatment, including, but not limited to,odor control in a wastewater treatment system; biological treatment ofBOD, TSS, NH₃, TN, and TP; digestion of waste solids, which may alsoinclude methane generation; and pre-dewatering conditioning and odorreduction of biosolids. Further, an effective amount of a dispersingagent and one or more of a free magnesium control agent and a seedmaterial may also be used in connection with wastewater treatment, forexample, to reduce the formation and/or collection of struvite scalewithin at least a portion of the wastewater treatment system. In someembodiments, an effective amount of a magnesium compound and aneffective amount of a free magnesium control agent may be used inconnection with wastewater treatment. In some embodiments, an effectiveamount of a magnesium compound, and effective amount of a free magnesiumcontrol agent, and an effective amount of a seed material may be used inconnection with wastewater treatment. In some embodiments, an effectiveamount of a magnesium compound and an effective amount of a seedmaterial (e.g., which include one or more of a micro-silica, aluminum,iron, titanium, tin, copper, molybdenum, manganese, lanthanum, selenium,zeolites, clay, and volcanic ash) may be used in connection withwastewater treatment. In some embodiments, an effective amount of ascale reducing agent may be included in combination with any of theforegoing.

In an example embodiment, magnesium hydroxide may be combined with oneor more of seed materials, one or more dispersing agents, and/or one ormore free magnesium control agents to reduce and/or prevent theformation of struvite scale in at least a portion of a wastewatertreatment system, for example, a centrate side stream process of awastewater treatment system, which may be designed to reduce ammonialevels in the centrate or filtrate arising from digested biosolids andsludge. For example, when a supernatant is separated from digestedwaste, the resultant centrate or filtrate may be recycled through one ormore wastewater treatment processes and/or may be treated in a sidestream process. The centrate may generally contain relatively highlevels of magnesium, ammonia and phosphate. Such relatively high levelsof magnesium, ammonia and phosphate may result in the precipitation ofstruvite, for example if the centrate is exposed to the appropriatecombinatorial conditions of pH for spontaneous formation and/or seedingfor catalytic formation. In some situations, the precipitated struviteresults in the formation of struvite scale and/or struvite as asuspended nutrient by-product.

As an example, in a side stream process that may be designed to reduceammonia levels, various alkalinity supplements may be utilized tomaintain pH stability of the side stream process. For example,biological reduction of ammonia, which may be referred to asnitrification, may produce various acids, such as nitric acid, nitrousacid, and carbonic acid. The production of such acids may generallyresult in a decrease in the pH of the centrate being processed and/or ofthe resulting effluent. As such side stream ammonia removal processes,such as a conventional nitrification process and/or any of severalproprietary processes such as the SHARON® process, produce acids, theseprocesses may require additional alkalinity to stabilize the pH of theprocess. In some situations, the combination of relatively high pH, thatmay result from alkalinity addition, and the presence of magnesium,ammonia and phosphate may lead to the formation of struvite scale. Theaddition of an effective amount of a dispersing agent and one or more ofa free magnesium control agent and a seed material may allow forefficient use of alkaline supplements, such as magnesium hydroxide, tostabilize the pH of the ammonia removal process (e.g., by which ammoniamay be removed from centrate), while reducing and/or controlling theformation of struvite scale.

For example, an admixture including a hydroxide slurry in combinationwith an effective amount of a dispersing agent and one or more of a freemagnesium control agent and a seed material may be added to wastewaterat one or more of several possible locations within the wastewatertreatment system (e.g., within the particular side stream wastewatertreatment process). Similarly, the magnesium hydroxide slurry, thedispersing agent, and the one or more of the free magnesium controlagent and the seed material may be separately added, and or added invarious sub-combinations, as the one or more locations within thewastewater treatment system (e.g., within the particular side streamwastewater treatment process). The injection point or points (i.e., thepoint or points at which the various materials may be added to thewastewater within the wastewater treatment system) may vary fordifferent application (e.g., to provide an effective concentration ofeach material at the desired location of activity), and the point orpoints of injection may be selected based upon, at least in part, thesite and the desired application. In the example of a process forremoving ammonia from centrate in a side stream process, the magnesiumcompound and the dispersing agent and the one or more of the freemagnesium control agent and the seed material may be added to wastewaterin the wastewater treatment system, for example, at the influent ofcentrate/filtrate to the side stream process. In another example, themagnesium compound, the dispersing agent and the one or more of the freemagnesium control agent and the seed material may be added to wastewaterwithin the wastewater treatment system at multiple points other than atthe influent of the centrate/filtrate. The selection of applicationpoints may be based upon, at least in part, consideration of alkalinityand pH profiles in relation to the reduction of ammonia through theprocess.

In another example, magnesium hydroxide may be combined with adispersing agent and one or more of a free magnesium control agent and aseed material to prevent and/or reduce the formation of struvite scalewithin digesters of a wastewater treatment system. For example, in awastewater treatment plant anaerobic digesters may be utilized to treatsolid waste received by, and/or produced by, the wastewater treatmentplant. In some situations, the digestion process may result inrelatively high levels of magnesium, ammonia, and/or phosphatecomponents in the supernatant, liquid portion, of the digested waste.The relatively high levels of magnesium, ammonia and/phosphatecomponents in the supernatant, when exposed to the appropriatecombinatorial conditions of pH for spontaneous formation and/or seedingfor catalytic formation, may experience the precipitation of struvite.Such precipitation of struvite may manifest as struvite scale (e.g.,which may form in the digester and/or in downstream equipment), or as asuspended nutrient by-product. Further, the digestion process maygenerate acids, and in a similar manner as various other biologicalwastewater treatment processes that may be utilized in wastewatertreatment plants (such as municipal wastewater treatment plants), analkaline source such as magnesium hydroxide, caustic soda, or lime, maybe desirably used as an alkaline supplement to improve overallperformance of the digestion process and/or operation of the wastewatertreatment system overall.

In a generally similar manner as described above, a dispersing agent andone or more of a free magnesium control agent and a seed material may beadded to wastewater within a digester to prevent and/or reduce theformation and/or collection of struvite scale within the digester and/orin downstream locations. In some embodiments, the dispersing agent andthe one or more of the free magnesium control agent and the seedmaterial may be added to the wastewater within the digester incombination with (e.g., and/or separately from) a magnesium compound,which may provide an alkaline source. Adding the dispersing agent andthe one or more of the free magnesium control agent and the seedmaterial (e.g., and the magnesium compound) to wastewater within thedigester may include adding the materials to the digester, adding thematerials at an upstream location (e.g., such that an effective amountmay be present in the digester), and/or at a downstream location fromthe digester (e.g., in a situation in which the conditions arising inand/or from the digester may tend to result in struvite scale formationdownstream from the digester).

In yet another example, a magnesium hydroxide material may be combined(and/or separately added) with a dispersing agent and one or more of afree magnesium control agent and a seed material to prevent and/orreduce struvite scale formation in centrate return lines. In such anembodiment, the dispersing agent and the one or more of the freemagnesium control agent and the seed material may be added to wastewaterwithin the centrate return lines and/or upstream of the centrate returnlines, to thereby prevent and/or reduce the formation of struvite scalewithin the centrate return line. Various additional and/or alternativeembodiments will be appreciated.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made. Accordingly, otherimplementations are within the scope of the following claims.

What is claimed is:
 1. A method for treating wastewater comprising:adding a magnesium compound to wastewater within a wastewater treatmentsystem, wherein the wastewater treatment system includes a municipalwastewater treatment system; and adding an effective amount of adispersing agent and a free magnesium control agent to wastewater withinthe wastewater treatment system to reduce the reaction of the magnesiumcompound to form struvite, and to control the formation of struvitescale within the wastewater treatment system.
 2. The method of claim 1,further comprising: measuring struvite scale formation within thewastewater treatment system; and adjusting a concentration of one ormore of the dispersing agent and the free magnesium control agent toreduce the struvite scale formation within the wastewater treatmentsystem.
 3. The method of claim 1, wherein adding the magnesium compound,and adding the effective amount of the dispersing agent and the freemagnesium control agent includes adding an admixture including themagnesium compound, and the effective amount of the dispersing agent andthe free magnesium control agent to wastewater within the wastewatertreatment system.
 4. The method of claim 1, including: adding themagnesium compound to wastewater at a first location within thewastewater treatment system; adding the effective amount of thedispersing agent and the free magnesium control agent to wastewater at asecond location within the wastewater treatment system different fromthe first location.
 5. The method of claim 1, wherein the magnesiumcompound includes magnesium hydroxide, and the magnesium hydroxideexhibits an alkaline magnesium hydroxide purity of between about 85% toabout 100%; a caustic magnesia activity of between about 50 seconds toabout 1440 minutes; a particle size of between about 0.1 micron to about50 microns; a specific surface area of between about 9 m²/g to about 200m²/g; and a stabilized residuals test value of between about 1 milligramto about 50 grams.
 6. The method of claim 1, wherein the magnesiumcompound includes magnesium oxide, and the magnesium oxide exhibits analkaline magnesium oxide purity of between about 85% to about 100%; acaustic magnesia activity of between about 50 seconds to about 1000seconds; a particle size of between about 0.1 micron to about 30microns; and a specific surface area of between about 9 m²/g to about300 m²/g.
 7. The method of claim 1, wherein the dispersing agentincludes one or more of a polyacrylate, a polyamide, a polyacrylamide, apolyphosphate, a polyethylene glycol ester, an ethoxylated alkyl phenol,an ethoxylated polyhydric alcohol, an ethoxylated polyhydric ether, andan ethoxylated polyhydric ester.
 8. The method of claim 1, wherein theeffective amount of the dispersing agent includes between about 0.01% toabout 90% of the dispersing agent relative to the weight of themagnesium compound.
 9. The method of claim 3, wherein the admixtureincludes a slurry including between about 0.01% to about 50% of thedispersing agent by weight of the slurry.
 10. The method of claim 1,wherein the free magnesium control agent includes one or more of a saltof a polyamine acetic acid, an acid of a polyamine acetic acid, anoxylate, a polyphosphonic acid, a polyphosphate, a gluconate, acarboxylate polymer, and a polyaspartic acid.
 11. The method of claim 1,wherein the effective amount of the free magnesium control agentincludes between about 0.01% to about 90% of the free magnesium controlagent relative to the weight of the magnesium compound.
 12. The methodof claim 3, wherein the admixture includes a slurry including betweenabout 0.01% to about 50% of the free magnesium control agent by weightof the slurry.
 13. A method for treating wastewater comprising: adding amagnesium compound to wastewater within a wastewater treatment system,wherein the wastewater treatment system includes a municipal wastewatertreatment system; and adding an effective amount of a dispersing agent,a free magnesium control agent, and a seed material, including one ormore of struvite seeds, aluminum, iron, titanium, tin, copper,molybdenum, manganese, lanthanum, selenium, clay, and volcanic ash, towastewater within the wastewater treatment system to reduce the reactionof the magnesium compound to form struvite, and to control the formationof struvite scale within the wastewater treatment system.
 14. The methodof claim 13, further comprising: measuring struvite scale formationwithin the wastewater treatment system; and adjusting a concentration ofone or more of the dispersing agent and the seed material to reduce thestruvite scale formation within the wastewater treatment system.
 15. Themethod of claim 13, wherein adding the magnesium compound, and addingthe effective amount of the dispersing agent and the seed materialincludes adding an admixture including the magnesium compound, and theeffective amount of the dispersing agent and the seed material towastewater within the wastewater treatment system.
 16. The method ofclaim 13, including: adding the magnesium compound to wastewater at afirst location within the wastewater treatment system; adding theeffective amount of the dispersing agent and the seed material towastewater at a second location within the wastewater treatment systemdifferent from the first location.
 17. The method of claim 13, whereinthe magnesium compound includes magnesium hydroxide, and the magnesiumhydroxide exhibits an alkaline magnesium hydroxide purity of betweenabout 85% to about 100%; a caustic magnesia activity of between about 50seconds to about 1440 minutes; a particle size of between about 0.1micron to about 50 microns; a specific surface area of between about 9m²/g to about 200 m²/g; and a stabilized residuals test value of betweenabout 1 milligram to about 50 grams.
 18. The method of claim 13, whereinthe magnesium compound includes magnesium oxide, and the magnesium oxideexhibits an alkaline magnesium oxide purity of between about 85% toabout 100%; a caustic magnesia activity of between about 50 seconds toabout 1000 seconds; a particle size of between about 0.1 micron to about30 microns; and a specific surface area of between about 9 m²/g to about300 m²/g.
 19. The method of claim 13, wherein the dispersing agentincludes one or more of a polyacrylate, a polyamide, a polyacrylamide, apolyphosphate, a polyethylene glycol ester, an ethoxylated alkylphenols, an ethoxylated polyhydric alcohol, an ethoxylated polyhydricether, and an ethoxylated polyhydric esters.
 20. The method of claim 13,wherein the effective amount of the dispersing agent includes betweenabout 0.01% to about 90% of the dispersing agent relative to the weightof the magnesium compound.
 21. The method of claim 15, wherein theadmixture includes a slurry including between about 0.01% to about 50%of the dispersing agent by weight of the slurry.
 22. The method of claim13, wherein the seed material includes a combination of micro-silica andaluminum.
 23. The method of claim 13, wherein the seed material includesparticles having a length of between about 0.2 microns to about 1.0millimeters.
 24. The method of claim 13, wherein the effective amount ofthe seed material includes between about 0.01% to about 90% of the seedmaterial relative to the weight of the magnesium compound.
 25. Themethod of claim 15, wherein the admixture includes a slurry includingbetween about 0.01% to about 50% of the seed material by weight of theslurry.
 26. A method for treating wastewater comprising: adding amagnesium compound to wastewater within a wastewater treatment system,wherein the wastewater treatment system includes a municipal wastewatertreatment system; and adding an effective amount of a dispersing agentand a free magnesium control agent, wherein the free magnesium controlagent includes one or more of a salt of a polyamine acetic acid, an acidof a polyamine acetic acid, a gluconate, and a polyaspartic acid, towastewater within the wastewater treatment system to reduce the reactionof the magnesium compound to form struvite, and to control the formationof struvite scale within the wastewater treatment system.
 27. The methodof claim 26, further comprising: measuring struvite scale formationwithin the wastewater treatment system; and adjusting a concentration ofthe dispersing agent to reduce the struvite scale formation within thewastewater treatment system.
 28. The method of claim 26, wherein addingthe magnesium compound, and adding the effective amount of thedispersing agent includes adding an admixture including the magnesiumcompound and the effective amount of the dispersing agent to wastewaterwithin the wastewater treatment system.
 29. The method of claim 26,including: adding the magnesium compound to wastewater at a firstlocation within the wastewater treatment system; adding the effectiveamount of the dispersing agent at a second location within thewastewater treatment system different from the first location.
 30. Themethod of claim 29, wherein the second location includes an upstreamlocation relative to the first location.
 31. The method of claim 30,wherein adding the effective amount of the dispersing agent at thesecond location includes pre-conditioning the wastewater within thewastewater treatment system to control the formation of struvite scalewithin the wastewater treatment system.
 32. The method of claim 30,further including adding a seed material at the second location withinthe wastewater treatment system.